Search for gravitational waves from low mass compact
binary coalescence in LIGO’s sixth science run and
Virgo’s science runs 2 and 3
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Citation
J. Abadie et al. (LIGO Scientific Collaboration, Virgo
Collaboration). "Search for gravitational waves from low mass
compact binary coalescence in LIGO’s sixth science run and
Virgo’s science runs 2 and 3" Physical Review D 85, 082002
(2012). © 2012 American Physical Society
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http://dx.doi.org/10.1103/PhysRevD.85.082002
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American Physical Society
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Final published version
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Thu May 26 06:33:16 EDT 2016
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http://hdl.handle.net/1721.1/71660
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PHYSICAL REVIEW D 85, 082002 (2012)
Search for gravitational waves from low mass compact binary coalescence in
LIGO’s sixth science run and Virgo’s science runs 2 and 3
J. Abadie,1,a B. P. Abbott,1,a R. Abbott,1,a T. D. Abbott,2,a M. Abernathy,3,a T. Accadia,4,b F. Acernese,5a,5c,b C. Adams,6,a
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S. M. Aston,14,a P. Astone,15a,b D. Atkinson,16,a P. Aufmuth,8,7,a C. Aulbert,7,8,a B. E. Aylott,14,a S. Babak,17,a P. Baker,18,a
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M. Benacquista,26,a J. M. Berliner,16,a A. Bertolini,7,8,a J. Betzwieser,1,a N. Beveridge,3,a P. T. Beyersdorf,27,a
I. A. Bilenko,28,a G. Billingsley,1,a J. Birch,6,a R. Biswas,26,a M. Bitossi,25a,b M. A. Bizouard,29a,b E. Black,1,a
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M. Britzger,7,8,a A. F. Brooks,1,a D. A. Brown,20,a A. Brummit,39,a T. Bulik,40b,40c,b H. J. Bulten,9a,9b,b A. Buonanno,41,a
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S. Chelkowski,14,a Y. Chen,48,a A. Chincarini,49,b A. Chiummo,19,b H. Cho,50,a N. Christensen,51,a S. S. Y. Chua,52,a
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M. Coughlin,51,a J.-P. Coulon,32a,b P. Couvares,20,a D. M. Coward,21,a D. C. Coyne,1,a J. D. E. Creighton,10,a
T. D. Creighton,26,a A. M. Cruise,14,a A. Cumming,3,a L. Cunningham,3,a E. Cuoco,19,b R. M. Cutler,14,a K. Dahl,7,8,a
S. L. Danilishin,28,a R. Dannenberg,1,a S. D’Antonio,55a,b K. Danzmann,7,8,a V. Dattilo,19,b B. Daudert,1,a H. Daveloza,26,a
M. Davier,29a,b G. Davies,54,a E. J. Daw,57,a R. Day,19,b T. Dayanga,34,a R. De Rosa,5a,5b,b D. DeBra,11,a G. Debreczeni,58,a
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S. Dhurandhar,60,a L. Di Fiore,5a,b A. Di Lieto,25a,25b,b I. Di Palma,7,8,a M. Di Paolo Emilio,55a,55c,b A. Di Virgilio,25a,b
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A. Effler,13,a P. Ehrens,1,a G. Endrőczi,58,a R. Engel,1,a T. Etzel,1,a K. Evans,3,a M. Evans,22,a T. Evans,6,a
M. Factourovich,24,a V. Fafone,55a,55b,b S. Fairhurst,54,a Y. Fan,21,a B. F. Farr,63,a W. Farr,63,a D. Fazi,63,a H. Fehrmann,7,8,a
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P. Fritschel,22,a V. V. Frolov,6,a P. J. Fulda,14,a M. Fyffe,6,a M. Galimberti,33,b L. Gammaitoni,35a,35b,b M. R. Ganija,66,a
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L. Á. Gergely,67,a S. Ghosh,34,a J. A. Giaime,13,6,a S. Giampanis,10,a K. D. Giardina,6,a A. Giazotto,25a,b C. Gill,3,a
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C. Greverie,32a,b R. Grosso,26,a H. Grote,7,8,a S. Grunewald,17,a G. M. Guidi,36a,36b,b C. Guido,6,a R. Gupta,60,a
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C. Hanna,1,70,a J. Hanson,6,a A. Hardt,51,a J. Harms,62,a G. M. Harry,22,a I. W. Harry,54,a E. D. Harstad,37,a M. T. Hartman,12,a
K. Haughian,3,a K. Hayama,71,a J.-F. Hayau,32b,b J. Heefner,1,a A. Heidmann,38,b M. C. Heintze,12,a H. Heitmann,32a,a
P. Hello,29a,b M. A. Hendry,3,a I. S. Heng,3,a A. W. Heptonstall,1,a V. Herrera,11,a M. Hewitson,7,8,a S. Hild,3,a D. Hoak,42,a
K. A. Hodge,1,a K. Holt,6,a T. Hong,48,a S. Hooper,21,a D. J. Hosken,66,a J. Hough,3,a E. J. Howell,21,a B. Hughey,10,a
S. Husa,72,a S. H. Huttner,3,a T. Huynh-Dinh,6,a D. R. Ingram,16,a R. Inta,52,a T. Isogai,51,a A. Ivanov,1,a K. Izumi,71,a
M. Jacobson,1,a H. Jang,73,a P. Jaranowski,40d,b W. W. Johnson,13,a D. I. Jones,74,a G. Jones,54,a R. Jones,3,a L. Ju,21,a
1550-7998= 2012=85(8)=082002(12)
082002-1
Ó 2012 American Physical Society
J. ABADIE et al.
1,a
PHYSICAL REVIEW D 85, 082002 (2012)
63,a
54,a
61,a
P. Kalmus, V. Kalogera,
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S. Kandhasamy,
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C. H. Lee,50,a H. M. Lee,78,a N. Leindecker,11,a J. R. Leong,7,8,a I. Leonor,37,a N. Leroy,29a,b N. Letendre,4,b J. Li,44,a
T. G. F. Li,9a,b N. Liguori,59a,59b,b P. E. Lindquist,1,a N. A. Lockerbie,79,a D. Lodhia,14,a M. Lorenzini,36a,b V. Loriette,29b,b
M. Lormand,6,a G. Losurdo,36a,b J. Luan,48,a M. Lubinski,16,a H. Lück,7,8,a A. P. Lundgren,31,a E. Macdonald,3,a
B. Machenschalk,7,8,a M. MacInnis,22,a D. M. Macleod,54,a M. Mageswaran,1,a K. Mailand,1,a E. Majorana,15a,b
I. Maksimovic,29b,b N. Man,32a,b I. Mandel,22,a V. Mandic,61,a M. Mantovani,25a,25c,b A. Marandi,11,a F. Marchesoni,35a,b
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N. Mavalvala,22,a G. Mazzolo,7,8,a R. McCarthy,16,a D. E. McClelland,52,a S. C. McGuire,80,a G. McIntyre,1,a J. McIver,42,a
D. J. A. McKechan,54,a G. D. Meadors,45,a M. Mehmet,7,8,a T. Meier,8,7,a A. Melatos,53,a A. C. Melissinos,81,a
G. Mendell,16,a D. Menendez,31,a R. A. Mercer,10,a S. Meshkov,1,a C. Messenger,54,a M. S. Meyer,6,a H. Miao,21,a
C. Michel,33,b L. Milano,5a,5b,b J. Miller,52,a Y. Minenkov,55a,b V. P. Mitrofanov,28,a G. Mitselmakher,12,a R. Mittleman,22,a
O. Miyakawa,71,a B. Moe,10,a P. Moesta,17,a M. Mohan,19,b S. D. Mohanty,26,a S. R. P. Mohapatra,42,a D. Moraru,16,a
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C. M. Mow-Lowry,52,a C. L. Mueller,12,a G. Mueller,12,a S. Mukherjee,26,a A. Mullavey,52,a H. Müller-Ebhardt,7,8,a
J. Munch,66,a D. Murphy,24,a P. G. Murray,3,a A. Mytidis,12,a T. Nash,1,a L. Naticchioni,15a,15b,b R. Nawrodt,3,a V. Necula,12,a
J. Nelson,3,a G. Newton,3,a A. Nishizawa,71,a F. Nocera,19,b D. Nolting,6,a L. Nuttall,54,a E. Ochsner,41,a J. O’Dell,39,a
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C. Osthelder,1,a C. D. Ott,48,a D. J. Ottaway,66,a R. S. Ottens,12,a H. Overmier,6,a B. J. Owen,31,a A. Page,14,a
G. Pagliaroli,55a,55c,b L. Palladino,55a,55c,b C. Palomba,15a,b Y. Pan,41,a C. Pankow,12,a F. Paoletti,25a,19,b M. A. Papa,17,10,a
M. Parisi,5a,5b,b A. Pasqualetti,19,b R. Passaquieti,25a,25b,b D. Passuello,25a,b P. Patel,1,a M. Pedraza,1,a P. Peiris,82,a
L. Pekowsky,20,a S. Penn,83,a C. Peralta,17,a A. Perreca,20,a G. Persichetti,5a,5b,b M. Phelps,1,a M. Pickenpack,7,8,a
F. Piergiovanni,36a,36b,b M. Pietka,40d,b L. Pinard,33,b I. M. Pinto,84,a M. Pitkin,3,a H. J. Pletsch,7,8,a M. V. Plissi,3,a
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S. Privitera,1,a R. Prix,7,8,a G. A. Prodi,59a,59b,b L. Prokhorov,28,a O. Puncken,7,8,a M. Punturo,35a,b P. Puppo,15a,b
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C. R. Ramet,6,a B. Rankins,46,a P. Rapagnani,15a,15b,b V. Raymond,63,a V. Re,55a,55b,b K. Redwine,24,a C. M. Reed,16,a
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F. Robinet,29a,b C. Robinson,54,a E. L. Robinson,17,a A. Rocchi,55a,b S. Roddy,6,a C. Rodriguez,63,a M. Rodruck,16,a
L. Rolland,4,b J. Rollins,24,a J. D. Romano,26,a R. Romano,5a,5c,b J. H. Romie,6,a D. Rosińska,40c,40f,b C. Röver,7,8,a
S. Rowan,3,a A. Rüdiger,7,8,a P. Ruggi,19,b K. Ryan,16,a H. Ryll,7,8,a P. Sainathan,12,a M. Sakosky,16,a F. Salemi,7,8,a
A. Samblowski,7,8,a L. Sammut,53,a L. Sancho de la Jordana,72,a V. Sandberg,16,a S. Sankar,22,a V. Sannibale,1,a
L. Santamarı́a,1,a I. Santiago-Prieto,3,a G. Santostasi,86,a B. Sassolas,33,b B. S. Sathyaprakash,54,a S. Sato,71,a
P. R. Saulson,20,a R. L. Savage,16,a R. Schilling,7,8,a S. Schlamminger,87,a R. Schnabel,7,8,a R. M. S. Schofield,37,a
B. Schulz,7,8,a B. F. Schutz,17,54,a P. Schwinberg,16,a J. Scott,3,a S. M. Scott,52,a A. C. Searle,1,a F. Seifert,1,a D. Sellers,6,a
A. S. Sengupta,1,a D. Sentenac,19,b A. Sergeev,75,a D. A. Shaddock,52,a M. Shaltev,7,8,a B. Shapiro,22,a P. Shawhan,41,a
D. H. Shoemaker,22,a A. Sibley,6,a X. Siemens,10,a D. Sigg,16,a A. Singer,1,a L. Singer,1,a A. M. Sintes,72,a G. Skelton,10,a
B. J. J. Slagmolen,52,a J. Slutsky,13,a J. R. Smith,2,a M. R. Smith,1,a N. D. Smith,22,a R. J. E. Smith,14,a K. Somiya,48,a
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J. Steinlechner,7,8,a S. Steinlechner,7,8,a S. Steplewski,34,a A. Stochino,1,a R. Stone,26,a K. A. Strain,3,a S. Strigin,28,a
A. S. Stroeer,26,a R. Sturani,36a,36b,b A. L. Stuver,6,a T. Z. Summerscales,88,a M. Sung,13,a S. Susmithan,21,a P. J. Sutton,54,a
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R. Taylor,1,a P. Thomas,16,a K. A. Thorne,6,a K. S. Thorne,48,a E. Thrane,61,a A. Thüring,8,7,a C. Titsler,31,a
K. V. Tokmakov,79,a A. Toncelli,25a,25b,b M. Tonelli,25a,25b,b O. Torre,25a,25c,b C. Torres,6,a C. I. Torrie,1,3,a E. Tournefier,4,b
F. Travasso,35a,35b,b G. Traylor,6,a M. Trias,72,a K. Tseng,11,a E. Tucker,51,a D. Ugolini,89,a K. Urbanek,11,a H. Vahlbruch,8,7,a
082002-2
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25a,25b,b
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PHYSICAL REVIEW D 85, 082002 (2012)
9a,9b,b
G. Vajente,
M. Vallisneri,
J. F. J. van den Brand,
C. Van Den Broeck,9a,b S. van der Putten,9a,b
A. A. van Veggel,3,a S. Vass,1,a M. Vasuth,58,a R. Vaulin,22,a M. Vavoulidis,29a,b A. Vecchio,14,a G. Vedovato,59c,b
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T. Westphal,7,8,a K. Wette,7,8,a J. T. Whelan,82,a S. E. Whitcomb,1,21,a D. White,57,a B. F. Whiting,12,a C. Wilkinson,16,a
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A. G. Wiseman,10,a H. Wittel,7,8,a G. Woan,3,a R. Wooley,6,a J. Worden,16,a J. Yablon,63,a I. Yakushin,6,a H. Yamamoto,1,a
K. Yamamoto,7,8,a H. Yang,48,a D. Yeaton-Massey,1,a S. Yoshida,90,a P. Yu,10,a M. Yvert,4,b A. Zadroźny,40e,b
M. Zanolin,68,a J.-P. Zendri,59c,b F. Zhang,44,a L. Zhang,1,a W. Zhang,44,a Z. Zhang,21,a C. Zhao,21,a N. Zotov,85,a
M. E. Zucker,22,a and J. Zweizig1,a
(aLIGO Scientific Collaboration)
(bVirgo Collaboration)
1
LIGO-California Institute of Technology, Pasadena, California 91125, USA
2
California State University Fullerton, Fullerton California 92831 USA
3
SUPA, University of Glasgow, Glasgow, G12 8QQ, United Kingdom
4
Laboratoire d’Annecy-le-Vieux de Physique des Particules (LAPP), , USAUniversité de Savoie,
CNRS/IN2P3, F-74941 Annecy-Le-Vieux, France
5a
INFN, Sezione di Napoli, Italy
5b
Università di Napoli ’Federico II’ Complesso Universitario di Monte S.Angelo, I-80126 Napoli, Italy
5c
Università di Salerno, Fisciano, I-84084 Salerno, Italy
6
LIGO-Livingston Observatory, Livingston, Louisiana 70754, USA
7
Albert-Einstein-Institut, Max-Planck-Institut für Gravitationsphysik, D-30167 Hannover, Germany
8
Leibniz Universität Hannover, D-30167 Hannover, Germany
9a
Nikhef, Science Park, Amsterdam, the Netherlands
9b
VU University Amsterdam, De Boelelaan 1081, 1081 HV Amsterdam, the Netherlands
10
University of Wisconsin-Milwaukee, Milwaukee, Wisconsin 53201, USA
11
Stanford University, Stanford, California 94305, USA
12
University of Florida, Gainesville, Florida 32611, USA
13
Louisiana State University, Baton Rouge, Louisiana 70803, USA
14
University of Birmingham, Birmingham, B15 2TT, United Kingdom
15a
INFN, Sezione di Roma, I-00185 Roma, Italy
15b
Università ’La Sapienza’, I-00185 Roma, Italy
16
LIGO-Hanford Observatory, Richland, Washington 99352, USA
17
Albert-Einstein-Institut, Max-Planck-Institut für Gravitationsphysik, D-14476 Golm, Germany
18
Montana State University, Bozeman, Montana 59717, USA
19
European Gravitational Observatory (EGO), I-56021 Cascina (PI), Italy
20
Syracuse University, Syracuse, New York 13244, USA
21
University of Western Australia, Crawley, WA 6009, Australia
22
LIGO-Massachusetts Institute of Technology, Cambridge, Massachusetts 02139, USA
23
APC, AstroParticule et Cosmologie, Université Paris Diderot, CNRS/IN2P3, CEA/Irfu, Observatoire de Paris,
Sorbonne Paris Cité, 10, rue Alice Domon et Léonie Duquet, 75205 Paris Cedex 13, France
24
Columbia University, New York, New York 10027, USA
25a
INFN, Sezione di Pisa, Italy
25b
Università di Pisa, I-56127 Pisa, Italy
25c
Università di Siena, I-53100 Siena, Italy
26
The University of Texas at Brownsville and Texas Southmost College, Brownsville,
Texas 78520, USA
27
San Jose State University, San Jose, California 95192, USA
28
Moscow State University, Moscow, 119992, Russia
29a
LAL, Université Paris-Sud, IN2P3/CNRS, F-91898 Orsay, USA
29b
ESPCI, CNRS, F-75005 Paris, France
30
NASA/Goddard Space Flight Center, Greenbelt, Maryland 20771, USA
31
The Pennsylvania State University, University Park, Pennsylvania 16802, USA
32a
Université Nice-Sophia-Antipolis, CNRS, Observatoire de la Côte d’Azur, F-06304 Nice, France
082002-3
J. ABADIE et al.
PHYSICAL REVIEW D 85, 082002 (2012)
32b
Institut de Physique de Rennes, CNRS, Université de Rennes 1, 35042 Rennes, France
Laboratoire des Matériaux Avancés (LMA), IN2P3/CNRS, F-69622 Villeurbanne, Lyon, France
34
Washington State University, Pullman, Washington 99164, USA
35a
INFN, Sezione di Perugia, Italy
35b
Università di Perugia, I-06123 Perugia, Italy
36a
INFN, Sezione di Firenze, I-50019 Sesto Fiorentino, Italy
36b
Università degli Studi di Urbino ’Carlo Bo’, I-61029 Urbino, Italy
37
University of Oregon, Eugene, Oregon 97403, USA
38
Laboratoire Kastler Brossel, ENS, CNRS, UPMC, Université Pierre et Marie Curie, 4 Place Jussieu,
F-75005 Paris, France
39
Rutherford Appleton Laboratory, HSIC, Chilton, Didcot, Oxon OX11 0QX United Kingdom
40a
IM-PAN 00-956 Warsaw, Poland
40b
Astronomical Observatory Warsaw University 00-478 Warsaw, Poland
40c
CAMK-PAN 00-716 Warsaw, Poland
40d
Białystok University 15-424 Białystok, Poland
40e
IPJ 05-400 Świerk-Otwock, Poland
40f
Institute of Astronomy 65-265 Zielona Góra, Poland
41
University of Maryland, College Park, Maryland 20742 USA
42
University of Massachusetts-Amherst, Amherst, Massachusetts 01003, USA
43
Canadian Institute for Theoretical Astrophysics, University of Toronto, Toronto,
Ontario, M5S 3H8, Canada
44
Tsinghua University, Beijing 100084 China
45
University of Michigan, Ann Arbor, Michigan 48109, USA
46
The University of Mississippi, University, Mississippi 38677, USA
47
Charles Sturt University, Wagga Wagga, NSW 2678, Australia
48
Caltech-CaRT, Pasadena, California 91125, USA
49
INFN, Sezione di Genova, I-16146 Genova, Italy
50
Pusan National University, Busan 609-735, Korea
51
Carleton College, Northfield, Minnesota 55057, USA
52
Australian National University, Canberra, ACT 0200, Australia
53
The University of Melbourne, Parkville, VIC 3010, Australia
54
Cardiff University, Cardiff, CF24 3AA, United Kingdom
55a
INFN, Sezione di Roma Tor Vergata, Italy
55b
Università di Roma Tor Vergata, I-00133 Roma, Italy
55c
Università dell’Aquila, I-67100 L’Aquila, Italy
56
University of Salerno, I-84084 Fisciano (Salerno), Italy and INFN (Sezione di Napoli), Italy
57
The University of Sheffield, Sheffield S10 2TN, United Kingdom
58
RMKI, H-1121 Budapest, Konkoly Thege Miklós út 29-33, Hungary
59a
INFN, Gruppo Collegato di Trento, Italy
59b
Università di Trento, I-38050 Povo, Trento, Italy
59c
INFN, Sezione di Padova, Italy
59d
Università di Padova, I-35131 Padova, Italy
60
Inter-University Centre for Astronomy and Astrophysics, Pune-411, India
61
University of Minnesota, Minneapolis, Minnesota 55455, USA
62
California Institute of Technology, Pasadena, California 91125, USA
63
Northwestern University, Evanston, Illinois 60208, USA
64
The University of Texas at Austin, Austin, Texas 78712, USA
65
Eötvös Loránd University, Budapest, 1117 Hungary
66
University of Adelaide, Adelaide, SA 5005, Australia
67
University of Szeged, 6720 Szeged, Dóm tér 9, Hungary
68
Embry-Riddle Aeronautical University, Prescott, Arizona 86301 USA
69
National Institute for Mathematical Sciences, Daejeon 305-390, Korea
70
Perimeter Institute for Theoretical Physics, Ontario, Canada, N2L 2Y5
71
National Astronomical Observatory of Japan, Tokyo 181-8588, Japan
72
Universitat de les Illes Balears, E-07122 Palma de Mallorca, Spain
73
Korea Institute of Science and Technology Information, Daejeon 305-806, Korea
74
University of Southampton, Southampton, SO17 1BJ, United Kingdom
75
Institute of Applied Physics, Nizhny Novgorod, 603950, Russia
76
Lund Observatory, Box 43, SE-221 00, Lund, Sweden
77
Hanyang University, Seoul 133-791, Korea
78
Seoul National University, Seoul 151-742, Korea
33
082002-4
SEARCH FOR GRAVITATIONAL WAVES FROM LOW MASS . . .
PHYSICAL REVIEW D 85, 082002 (2012)
79
University of Strathclyde, Glasgow, G1 1XQ, United Kingdom
Southern University and A&M College, Baton Rouge, Louisiana 70813, USA
81
University of Rochester, Rochester, New York 14627, USA
82
Rochester Institute of Technology, Rochester, New York 14623, USA
83
Hobart and William Smith Colleges, Geneva, New York 14456, USA
84
University of Sannio at Benevento, I-82100 Benevento, Italy and INFN (Sezione di Napoli), Italy
85
Louisiana Tech University, Ruston, Louisiana 71272, USA
86
McNeese State University, Lake Charles, Louisiana 70609 USA
87
University of Washington, Seattle, Washington, 98195-4290, USA
88
Andrews University, Berrien Springs, Michigan 49104 USA
89
Trinity University, San Antonio, Texas 78212, USA
90
Southeastern Louisiana University, Hammond, Louisiana 70402, USA
(Received 16 December 2011; published 19 April 2012)
80
We report on a search for gravitational waves from coalescing compact binaries using LIGO and Virgo
observations between July 7, 2009, and October 20, 2010. We searched for signals from binaries with total
mass between 2 and 25M ; this includes binary neutron stars, binary black holes, and binaries consisting
of a black hole and neutron star. The detectors were sensitive to systems up to 40 Mpc distant for binary
neutron stars, and further for higher mass systems. No gravitational-wave signals were detected. We report
upper limits on the rate of compact binary coalescence as a function of total mass, including the results
from previous LIGO and Virgo observations. The cumulative 90% confidence rate upper limits of the
binary coalescence of binary neutron star, neutron star-black hole, and binary black hole systems are
1:3 104 , 3:1 105 , and 6:4 106 Mpc3 yr1 , respectively. These upper limits are up to a factor
1.4 lower than previously derived limits. We also report on results from a blind injection challenge.
DOI: 10.1103/PhysRevD.85.082002
PACS numbers: 04.30.Db, 04.80.Cc
I. INTRODUCTION
During 2009 and 2010, both the Laser Interferometer
Gravitational-wave Observatory (LIGO) [1] and Virgo [2]
gravitational-wave detectors undertook science runs with
better sensitivity across a broader range of frequencies than
previously achieved. Among the most promising sources of
gravitational waves for these detectors are compact stellar
mass binaries as they spiral in toward each other and
merge. For such systems, which include binary neutron
stars (BNS), binary black holes (BBH), and neutron starblack hole binaries (NSBH), the late stages of inspiral and
merger occur in the most sensitive band (between 40 and
1000 Hz) of the LIGO and Virgo detectors. In this paper,
we report on a search for gravitational waves from binary
systems with a maximum total mass of 25M , and a
minimum component mass of 1M .
A hardware injection was performed during the data
collection without the knowledge of the data analysis
teams as part of a ‘‘blind injection challenge’’ [3]. This
challenge was intended to test the data analysis procedures
and processes for evaluating candidate events. The injection was performed by coherently actuating the mirrors
on the LIGO and Virgo detectors to mimic a gravitationalwave signal. Prior to its unveiling as an injection
(‘‘unblinding’’), the event was determined to be a candidate gravitational wave: it was found to have a false alarm
rate of less than 1 in 7000 yr and no evidence for an
instrumental or environmental origin could be found.
After the analysis of the event was finished it was revealed
to be a blind injection and removed from the data.
With the blind injection removed there were no gravitational waves observed above the noise background. As a
result we place upper limits on rates of compact binary
coalescence (CBC), using upper limits from previous
gravitational-wave searches [4] as prior information. The
upper limits presented here are up to a factor 1.4 lower than
previously derived limits but still 2 to 3 orders of magnitude above expected CBC rates [5].
The paper is laid out as follows. In Sec. II, we provide a
brief description of the detectors and their sensitivities
during LIGO’s sixth science run (S6) and Virgo’s second
and third science runs. In Sec. III we present a brief overview of the analysis methods used in performing the
search. In Sec. IV we discuss the recovery of the blind
injection. In Sec. V we present the results of the search
with the blind injection removed. In Sec. VI we give the
upper limits obtained from the search and close with a brief
discussion in Sec. VII.
II. DETECTORS
LIGO comprises two sites, one in Hanford, Washington,
and the second in Livingston, Louisiana. The data used in
this search were taken during S6, which took place between July 7, 2009, and October 20, 2010. During S6 each
of these sites operated a single 4 km laser interferometer,
denoted as H1 and L1, respectively. The 2 km H2 instrument at the Hanford site which operated in earlier science
runs was not operational in S6. Following LIGO’s fifth
science run (S5) [1], several hardware changes were
made to the LIGO detectors so that prototypes of advanced
082002-5
J. ABADIE et al.
PHYSICAL REVIEW D 85, 082002 (2012)
FIG. 1 (color online). Typical detector strain noise spectral
density for the LIGO S6 and Virgo VSR2/3 runs. From lowest
to highest at 102 Hz, the curves are for the H1, L1, and V1
detectors.
LIGO technology could be installed and tested [6,7]. This
included the installation of a higher power laser, and the
implementation of a DC readout system that included a
new output mode cleaner on an advanced LIGO seismic
isolation table [8]. In addition, the hydraulic seismic isolation system was improved by fine-tuning its feed-forward
path.
The Virgo detector (denoted V1) is a single, 3 km laser
interferometer located in Cascina, Italy. The data used in
this search were taken from both Virgo’s second science
run (VSR2), which ran from July 7, 2009, to January 8,
2010, and its third science run (VSR3), which ran from
August 11, 2010, to October 20, 2010. In the period
between the first Virgo science run (VSR1) and VSR2,
several enhancements were made to the Virgo detector.
Specifically, a more powerful laser was installed in
Virgo, along with a thermal compensation system
and improved scattered light mitigation. During early
2010, monolithic suspensions were installed, which involved replacing Virgo’s test masses with new mirrors
hung from fused-silica fibers [9]. VSR3 followed this
upgrade.
The sensitivity of the detectors during the S6, VSR2, and
VSR3 runs is shown in Fig. 1. The corresponding sensitivity to binary coalescence signals is shown in Fig. 2. This
figure shows the distance at which an optimally oriented
and located binary would produce a signal-to-noise ratio
(SNR) of 8 in a given detector. The figure illustrates the
improvement in sensitivity for the LIGO detectors between
S5 and S6 and for Virgo between VSR1 and VSR2. The
reduction in the horizon distance of the Virgo detector in
VSR3 is due to a mirror with an incorrect radius of curvature being installed during the conversion to monolithic
suspension.
FIG. 2 (color online). Inspiral horizon distance versus the total
mass of equal-mass binaries from S5/VSR1 and S6/VSR2/VSR3.
The horizon distance is the distance at which an optimally
located and oriented binary would produce an expected
signal-to-noise ratio of 8. The figure shows the best sensitivity
achieved by each detector during the runs.
III. BINARY COALESCENCE SEARCH
To search for gravitational waves from compact binary
coalescence [4,10,11], we use matched filtering to correlate the detector’s strain output with a theoretical model of
the gravitational waveform [12]. Each detector’s output is
separately correlated against a bank [13] of template waveforms generated at 3.5 post-Newtonian order in the frequency domain [14,15]. Templates were laid out across the
mass range such that no more than 3% of the SNR was lost
due to the discreteness of the bank. Only nonspinning
waveforms with zero eccentricity and a component mass
1M were generated, and the templates were terminated
prior to merger. In the early stages of the run, as in previous
searches [4,10,11], the template bank included waveforms
from binaries with a total mass M 35M . However, the
search results indicated that the higher mass templates
(M > 25M ) were more susceptible to nonstationary noise
in the data. Furthermore, it is at these higher masses where
the merger and ringdown phases of the signal come into the
detectors’ sensitive bands. Consequently, the upper mass
limit of this search was reduced to 25M during the latter
stages of the science run. Results of a search for higher
mass binary black holes using nonspinning, full coalescence (inspiral-merger-ringdown) template waveforms,
such as in [16], will be presented in a future publication.
Although the template waveforms in this search neglect the
spin of the binary components, the search is still capable of
detecting binaries whose waveforms are modulated by the
effect of spin [17].
We require candidate signals to have a matched-filter
SNR greater than 5.5 in at least two detectors, and to have
082002-6
SEARCH FOR GRAVITATIONAL WAVES FROM LOW MASS . . .
consistent values of template masses and time of arrival
(allowing for travel-time difference) across the detectors
where this threshold is exceeded [18]. We use a chi-squared
test [19] to suppress non-Gaussian noise transients, which
have a high SNR but whose time-frequency evolution is
inconsistent with the template waveform. If the reduced
chi-squared of a signal, 2r , is greater than unity, we reweight the SNR in order to suppress the significance of
false signals, obtaining a reweighted SNR statistic1
for 2r > 1;
2 3
1=6
^ ¼ ½ð1þðr Þ Þ=2
(1)
for 2r 1:
Our analysis reports the coalescence time and the quadrature sum, c , of reweighted SNRs for events coincident
between the detectors. The statistic c is then used to rank
events by their significance above the expected background. To measure the background rate of coincident
events in the search, we time-shift data from the detectors
by an amount greater than the gravitational-wave traveltime difference between detector sites and reanalyze the
data. Many independent time-shifts are performed to obtain
a good estimate of the probability of accidental coincidence
of noise transients at two or more sites.
The background rates of coincident events were initially
estimated using 100 time-shifted analyses. These background rates vary depending on the binary’s mass—via
the waveform duration and frequency band—and also on
the detectors involved in the coincidence (the event type).
The relevant mass parameter is the binary’s chirp mass,
M ðm1 m2 Þ3=5 ðm1 þ m2 Þ1=5 , where m1 and m2 are the
component masses in the binary system. Thus, we sort
coincident events into three bins by chirp mass and by
event type [10].
The requirement of a coincident signal between at least
two sites restricts the times that can be analyzed to four
distinct types of coincident time. Between July 2009 and
October 2010, a total of 0.56 yr of two-or-more-site coincident data was collected. This comprised 0.14 yr of
H1L1V1 coincident data, 0.21 yr of H1L1 data, 0.13 yr
of H1V1 data, and 0.08 yr of L1V1 data. During H1L1V1
coincident time there are four distinct event types:
H1L1V1, H1L1, H1V1, and L1V1. In S6/VSR2, all four
event types were kept. In S6/VSR3, H1V1 and L1V1
events in triple-coincident time were discarded due to the
heightened rate of transient noise artifacts in Virgo and its
decreased sensitivity.
For each candidate, a false alarm rate (FAR) is computed
by comparing its c value to background events in the
same mass bin and coincident time and with the same
event type. Candidates’ FAR values are then compared to
1
Equation (1) is an improvement over the ‘‘effective SNR’’
used to rank events in [4,10,11]. Most notably, while effective
SNR also reweighted SNR using 2r , it became larger than SNR
when 2r < 1. This made it susceptible to overweighting events
that had statistical downward fluctuations in 2r .
PHYSICAL REVIEW D 85, 082002 (2012)
background events in all bins and event types, over the
appropriate coincident time, to calculate a combined FAR.
This is the detection statistic which is used to assess the
significance of events over the entire analysis time.
Because of the finite number of time-shifts performed,
the smallest nonzero FAR that can be calculated is 1=Tbg ,
where Tbg is the total background time obtained by summing the coincident live time in each time-shift. If an event
was found to be louder than all background events within
its analysis period, additional time-shifted analyses were
performed to calculate a more precise FAR for the event.
Although the detectors are enclosed in vacuum systems
and isolated from vibrational, acoustic, and electromagnetic disturbances, their typical output data contain a larger
number of transient noise events (glitches) with higher
amplitude than expected from Gaussian processes alone.
Each observatory is equipped with a system of environmental and instrumental monitors that are sensitive to
glitch sources but have a negligible sensitivity to gravitational waves. These sensors were used to identify times
when the detector output was potentially corrupted
[20–23]. We grouped these times into two categories:
periods with well-understood couplings between nongravitational-wave sources and detector output, and periods when a statistical correlation was found but a coupling
mechanism was not identified. In our primary search—
which included the identification of gravitational-wave
candidates and the calculation of upper limits—we removed (vetoed) from the analysis times that fell in either
of the two categories, along with any coincident events that
occurred during these periods. We also performed a secondary search for possible loud candidate events, in which
only the times with known couplings were vetoed.
Approximately 10% of the data, designated playground,
was used for tuning and data quality investigations. These
data were searched for gravitational waves, but not used in
calculating upper limits. After all vetoes were applied and
playground time excluded, there was 0.09 yr of H1L1V1
time, 0.17 yr of H1L1 time, 0.10 yr of H1V1 time, and
0.07 yr of L1V1 time, giving a total analysis time of 0.43 yr.
A substantial change from the analysis procedure of [11]
was that data were analyzed in two-week blocks with a
latency of two to four weeks, to allow for feedback of
information to ongoing detector characterization efforts
and to improve data quality. Thus, during the search
many new vetoes were introduced resulting from improved
understanding of the detectors. However, significant numbers of delta-function-like glitches with large amplitudes
remained unvetoed in the LIGO detectors. These were
found to cause artifacts in the matched-filter output over
a short time surrounding the glitch: thus, during the latter
stages of the search, 8 s of time on either side of any
matched-filter SNR exceeding 250 was vetoed. Times
removed from the primary search by this veto were still
examined for possible loud events.
082002-7
J. ABADIE et al.
PHYSICAL REVIEW D 85, 082002 (2012)
IV. BLIND INJECTION RECOVERY
The search pipeline described above identified a
gravitational-wave candidate occurring on September 16,
2010, at 06:42:23 UTC, with c ¼ 12:5 in coincidence
between the two LIGO detectors in the middle mass bin
3:48 M=M < 7:40. The highest matched-filter SNR
obtained in the search was 15 at M ¼ 4:7M in H1 and
10 at M ¼ 4:4M in L1. This difference in SNRs is
consistent with typical differences in antenna response
factors for these differently oriented detectors. Virgo was
also operating at the time of the event, but its sensitivity
was a factor of approximately 4 lower than the LIGO
detectors; the absence of a signal in Virgo above the
single-detector SNR threshold of 5.5 was consistent with
this fact. In the LIGO detectors, the signal was louder than
all time-shifted H1L1 coincident events in the same mass
bin throughout S6. However, with only 100 time-shifts, we
could only bound the FAR to <1=23 yr, even when folding
in all data from the entire analysis. To obtain a better
estimate of the event’s FAR we performed all possible
multiples of 5 sec time-shifts on four calendar months of
data around the event, corresponding to an effective analysis time of 2:0 105 yr. We found five events with a value
of c equal to or larger than the candidate’s, as shown in
Fig. 3. These five events were all coincidences between the
candidate’s signal in H1 and time-shifted transient noise in
L1. When we excluded 8 sec from around the event’s time
in the background estimation, we found no background
events with c greater than the candidate and we obtained a
significantly different background distribution, also shown
in Fig. 3.
Including the events at the time of the candidate in the
background estimate, the FAR of the event in the 3:48 M=M < 7:40 mass bin, coincident in the LIGO detectors, was estimated to be 1 in 4 104 yr. Since this event
occurred in H1L1V1 time during VSR3, only two event
types were considered: H1L1 double-coincident events and
H1L1V1 triple-coincident events. This resulted in a trials
factor of 6 (accounting for the three mass bins and two
coincidence types) and a combined FAR of 1 in 7000 yr.
The false alarm probability of this event in this analysis,
over the 0.47 yr of coincident time remaining after all
vetoes were applied, was 7 105 .
The detectors’ environmental monitoring channels record data from seismometers, accelerometers, microphones, magnetometers, radio receivers, weather sensors,
and a cosmic ray detector. Injections of environmental
signals and other tests indicate that these channels are
much more sensitive to environmental signals than the
gravitational-wave readout channels are. Arrays of these
detectors were operating and providing full coverage at the
time of the event, and did not record environmental signals
that could account for the event. Environmental signal
levels at our observatories and at external electromagnetic
weather observatories were typical of quiet times.
FIG. 3 (color online). The cumulative rate of events with chirp
mass 3:48 M=M < 7:40 coincident in the H1 and L1 detectors, seen in four months of data around the September 16
candidate, as a function of the threshold ranking statistic c . The
blue triangles show coincident events. Black dots show the
background estimated from 100 time-shifts. Black crosses
show the extended background estimation from all possible
5 sec shifts on this data restricted, for computational reasons,
to only the tail of loudest events. The gray dots and crosses show
the corresponding background estimates when 8 sec of data
around the time of the candidate are excluded. Gray shaded
contours show the 1-5 (dark to light) consistency of coincident
events with the estimated background including the extended
background estimate, for the events and analysis time shown,
including the candidate time. This event was later revealed to
have been a blind injection.
Mechanisms that could cause coincident signals among
widely separated detectors—such as earthquakes, microseismic noise due to large weather systems, and electromagnetic disturbances in the ionosphere [24,25]—were
therefore ruled out.
A loud transient occurred in L1 9 sec before the coalescence time of the signal. That transient belonged to a
known family of sharp ( 10 ms) and loud (SNR 200–80 000) glitches that appear 10–30 times per day in
the output optical sensing system of this detector. Since the
candidate signal swept through the sensitive band of the
detector, from 40 Hz to coalescence, in less than 4 sec, it
did not overlap the loud transient. Studies, including reanalysis of the data with the glitch removed, indicated that the
signal was not related to the earlier instrumental glitch. No
evidence was found that the observed signal was associated
with, or corrupted by, any instrumental effect.
Following the completion of this analysis, the event was
revealed to be a blind injection. While the analysis groups
did not know the event was an injection prior to its unblinding, they did know that one or more blind injections
may be performed during the analysis period. Such blind
injections have been carried out before: see [4] for the
082002-8
SEARCH FOR GRAVITATIONAL WAVES FROM LOW MASS . . .
results of a blind injection performed in a previous run.
This event was the only coherent CBC blind injection
performed during S6 and VSR2 and VSR3. The injection
was identified as a gravitational-wave candidate with high
probability, and the blind injection challenge was considered to be successful [3].
In order to more accurately determine the parameters
of the event prior to the unblinding, we performed
coherent Bayesian analyses of the data using models of
both spinning and nonspinning compact binary objects
[26–30]. These analyses showed evidence for the presence
of a weak signal in Virgo, consistent with the signal seen
by the two LIGO detectors. The strength of a signal in
Virgo is an important input to the localization of a source in
the sky. Parameter estimates varied significantly depending
on the exact model used for the gravitational waveform,
particularly when we included spin effects. However,
conservative unions of the confidence intervals from the
different waveform models were consistent with most injected parameters, including chirp mass, time of coalescence, and sky location. In addition, the signal was
correctly identified as having at least one highly spinning
component with the spin misaligned with the angular
orbital momentum. We will describe the details of parameter estimation on this and other CBC injections in a future
paper.
V. SEARCH RESULTS
After the event was revealed to be a blind injection the
data containing it were removed from the analysis. With
the injection excluded, there were no gravitational-wave
candidates observed in the data. Indeed the search result
was consistent with the background estimated from timeshifting the data. The most significant event was an L1V1
coincidence in L1V1 time with a combined FAR of
1:2 yr1 . The second and third most significant events
had combined FARs of 2:2 yr1 and 5:6 yr1 , respectively.
All of these events were consistent with background:
having analyzed 0:5 yr of data, we would expect the
loudest event to have a FAR of 2 2 yr1 . Although
PHYSICAL REVIEW D 85, 082002 (2012)
no detection candidates were found, a detailed investigation of the loudest events in each analysis period was
performed, to improve our understanding of instrumental
data quality.
VI. BINARY COALESCENCE RATE LIMITS
Given the absence of gravitational-wave signals, we
used our observations to set upper limits on coalescence
rates of BNS, BBH, and NSBH systems. We used the
procedure described in [31–33] to compute Bayesian
90% confidence level upper limits on the coalescence
rate for the various systems, making use of previous results
[4,10,11] as prior information on the rates.
The rate of binary coalescences in a spiral galaxy is
expected to be proportional to the star formation rate,
and hence blue light luminosity, of the galaxy [34].
Previous searches [4,10,11] presented upper limits in terms
1
of blue light luminosity, using units of L1
10 yr , where
one L10 is 1010 times the solar blue light luminosity. There
are, however, numerous challenges to evaluating the upper
limit as a function of luminosity, not least due to the large
uncertainties in both the luminosity of and distance to
nearby galaxies, as well as the lack of a complete galaxy
catalogue at larger distances [31,34]. On large scales
(greater than 20 Mpc), the luminosity per unit volume
is approximately constant; consequently the analysis can
be simplified by reporting upper limits per unit volume per
unit time. During the current analysis, the sensitivity of the
detectors to the systems of interest (as shown in Fig. 2) was
sufficiently large that we could assume signals were uniformly distributed in volume. We therefore quote upper
limits in units of Mpc3 yr1 . To incorporate the previous
results as prior distributions, we converted from L10 to
Mpc3 using a conversion factor of 0:02L10 per Mpc3 [34].
We estimate the volume to which the search is sensitive
by reanalyzing the data with the addition of a large number
of simulated signals (‘‘software injections’’) in order to
model the source population. Our ability to detect a signal
depends upon the parameters of the source, including the
component masses, the distance to the binary, its sky
TABLE I. Rate upper limits of BNS, NSBH, and BBH coalescence, assuming canonical mass
distributions. Dhorizon is the horizon distance averaged over the time of the search. The sensitive
distance averaged over all sky locations and binary orientations is Davg ’ Dhorizon =2:26 [35]. The
first set of upper limits is those obtained for binaries with nonspinning components. The second
set of upper limits is produced using black holes with a spin uniformly distributed between zero
and the maximal value of Gm2 =c.
System
Component masses (M )
Dhorizon (Mpc)
Nonspinning upper limit (Mpc3 yr1 )
Spinning upper limit (Mpc3 yr1 )
BNS
NSBH
BBH
1:35=1:35
40
1:3 104
1:35=5:0
80
3:1 105
3:6 105
5:0=5:0
90
6:4 106
7:4 106
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J. ABADIE et al.
PHYSICAL REVIEW D 85, 082002 (2012)
location, and its orientation with respect to the detectors.
Numerous signals with randomly chosen parameters were
therefore injected into the data. To compute the sensitive
volume for a given binary mass, we perform a Monte Carlo
integration over the other parameters to obtain the efficiency of the search—determined by the fraction of simulated signals found louder than the loudest foreground
event—as a function of distance. Integrating the efficiency
as a function of distance then gives the sensitive volume.
We consider several systematic uncertainties that
limit the accuracy of the measured search volume and
therefore the upper limits [10]: detector calibration errors
(conservatively estimated to be 14% in sensitive distance
combined over all three detectors and over the entire observational period, and a 2% bias correction), waveform
errors (taken to be a one-sided 10% [31] bias toward lower
sensitive distance), and Monte Carlo statistical errors
(3–5% in sensitive volume). We convert the sensitive distance uncertainties to volume uncertainties, and then marginalize over the uncertainty in volume to obtain an upper
limit which takes into account these systematic uncertainties [31].
In Table I we present the marginalized upper limits
at the 90% confidence level assuming canonical mass
distributions for nonspinning BNS (m1 ¼ m2 ¼
1:35 0:04M ), BBH (m1 ¼ m2 ¼ 5 1M ), and
NSBH (m1 ¼ 1:35 0:04M , m2 ¼ 5 1M ) systems.
We also compute upper limits as a function of total mass
M, using an injection population distributed uniformly
over M and uniformly over m1 for a given M. For
NSBH systems we present the upper limit as a function
of black hole mass, keeping the neutron-star mass fixed in
the range 1–3M . These are presented in Fig. 4. Figure 5
compares the upper limits obtained in this analysis (dark
gray regions) to limits obtained in our previous searches
up to S5/VSR1 [4] (light gray region) and to astrophysically predicted rates (hatched regions) for BNS, NSBH,
and BBH systems. The improvement over the previous
limits is up to a factor of 1.4, depending on binary mass;
this reflects the additional observation time and improved
sensitivity of the S6/VSR2/VSR3 data with respect to all
previous observations.
Although we searched with a bank of nonspinning templates, we compute upper limits for NSBH and BBH
systems in which one or both of the component masses
are spinning. These results are also presented in Table I.
We did not compute upper limits for spinning BNS systems
because astrophysical observations indicate that neutron
stars cannot have large enough spin to significantly affect
waveforms observable in the LIGO frequency band
[36,37]. Black hole spins were uniformly distributed in
both orientation and magnitude, S, with S constrained to
the range 0 S Gm2 =c, and m is the mass of the black
hole. As can be seen in Table I, the spinning upper limits
are 16% larger than nonspinning. Signals from spinning
FIG. 4. The marginalized upper limits as a function of mass. The
top plot shows the limit as a function of total mass M, using a
distribution uniform in m1 for a given M. The lower plot shows the
limit as a function of the black hole mass, with the neutron star
mass restricted to the range 1–3M . The light gray bars indicate
upper limits from previous searches. The dark bars indicate the
combined upper limits including the results of this search.
systems are recovered with a worse match to our templates
since we use a nonspinning template bank.
While the rates presented here represent an improvement over the previously published results from
earlier LIGO and Virgo science runs, they are still above
the astrophysically predicted rates of binary coalescence.
There are numerous uncertainties involved in estimating
astrophysical rates, including limited numbers of observations and unknown model parameters; consequently
the rate estimates are rather uncertain. For BNS
systems the estimated rates vary between 1 108
and 1 105 Mpc3 yr1 , with a ‘‘realistic’’ estimate of
1 106 Mpc3 yr1 . For BBH and NSBH, realistic estimates of the rate are 5 109 Mpc3 yr1 and
3 108 Mpc3 yr1 with at least an order of magnitude
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SEARCH FOR GRAVITATIONAL WAVES FROM LOW MASS . . .
FIG. 5 (color online). Comparison of CBC upper limit rates for
BNS, NSBH, and BBH systems. The light gray regions display
the upper limits obtained in the S5/VSR1 analysis; dark gray
regions show the upper limits obtained in this analysis, using the
S5/VSR1 limits as priors. The new limits are up to a factor of 1.4
improvement over the previous results. The lower (blue hatched)
regions show the spread in the astrophysically predicted rates,
with the dashed-black lines showing the realistic estimates [5].
Note: in Ref. [5], NSBH and BBH rates were quoted using a
black hole mass of 10M . We have therefore rescaled the S5 and
S6 NSBH and BBH upper limits in this plot by a factor of
ðM5 =M10 Þ5=2 , where M10 is the chirp mass of a binary in
which the black hole mass is 10M and M5 is the chirp mass of
a binary in which the black hole mass is 5M .
uncertainty in either direction [5]. In all cases, the upper
limits derived here are 2 to 3 orders of magnitude above the
realistic estimated rates, and about a factor of 10 above the
most optimistic predictions. These results are summarized
in Fig. 5.
VII. DISCUSSION
We performed a search for gravitational waves from
compact binary coalescences with total mass between 2
and 25M with the LIGO and Virgo detectors using data
taken between July 7, 2009, and October 20, 2010. No
gravitational waves candidates were detected, and we
placed new upper limits on CBC rates. These new limits
are up to a factor of 1.4 improvement over those achieved
using previous LIGO and Virgo observational runs up to
S5/VSR1 [4], but remain 2 to 3 orders of magnitude above
the astrophysically predicted rates.
The installation of the advanced LIGO and Virgo detectors has begun. When operational, these detectors will
provide a factor of 10 increase in sensitivity over the initial
detectors, providing a factor of 1000 increase in the
sensitive volume. At that time, we expect to observe tens
of binary coalescences per year [5].
In order to detect this population of gravitational-wave
signals, we will have to be able to confidently discriminate
it from backgrounds caused by both stationary and
PHYSICAL REVIEW D 85, 082002 (2012)
transient detector noise. It is customary [5] to assume
that a signal with SNR of 8 in each detector would stand
far enough above background that we would consider it to
be a detection candidate. The blind injection had somewhat
larger SNR than 8 in each detector, and we were able
estimate a FAR of 1 in 7000 yr for that event.
Alternatively, consider a coincident signal with exactly
SNR of 8 in two detectors. Provided the signal is a good
match to the template waveform (2r 1 in Eq. (1)) this
corresponds to c ¼ 11:3. As can be seen from the extended background events with the blind injection removed
in Fig. 3 (light gray crosses), this gives a FAR of 1 in
2 104 yr in a single trial, or 1 in 3000 yr over all trials.
Achieving similar-or-better background distributions in
Advanced LIGO and Virgo will require detailed data quality studies of the detectors and feedback from the CBC
searches, along with well-tuned signal-based vetoes. We
have continued to develop the pipeline with these goals in
mind. For this analysis we significantly decreased the
latency between taking data and producing results, which
allowed data quality vetoes to be finely tuned for the CBC
search. These successes, along with the successful recovery of the blind injection, give us confidence that we will be
able to detect gravitational waves from CBCs at the expected rates in Advanced LIGO and Virgo.
ACKNOWLEDGMENTS
The authors gratefully acknowledge the support of the
United States National Science Foundation for the construction and operation of the LIGO Laboratory, the
Science and Technology Facilities Council of the United
Kingdom, the Max-Planck-Society, and the State of
Niedersachsen/Germany for support of the construction
and operation of the GEO600 detector, and the Italian
Istituto Nazionale di Fisica Nucleare and the French
Centre National de la Recherche Scientifique for the construction and operation of the Virgo detector. The authors
also gratefully acknowledge the support of the research by
these agencies and by the Australian Research Council,
the International Science Linkages program of the
Commonwealth of Australia, the Council of Scientific
and Industrial Research of India, the Istituto Nazionale di
Fisica Nucleare of Italy, the Spanish Ministerio de
Educación y Ciencia, the Conselleria d’Economia
Hisenda i Innovació of the Govern de les Illes Balears,
the Foundation for Fundamental Research on Matter supported by the Netherlands Organisation for Scientific
Research, the Polish Ministry of Science and Higher
Education, the FOCUS Programme of Foundation for
Polish Science, the Royal Society, the Scottish Funding
Council, the Scottish Universities Physics Alliance, the
National Aeronautics and Space Administration, the
Carnegie Trust, the Leverhulme Trust, the David and
Lucile Packard Foundation, the Research Corporation,
and the Alfred P. Sloan Foundation.
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